This invention relates to the treatment of waste gases. In another aspect of the invention it relates to the recovery of manganese dioxide from a spent absorbent. In a specific aspect of the invention it relates to the use of ion exchange resins in the recovery of manganese compounds. In another specific aspect of the invention it relates to a process for removing oxides of sulphur and nitrogen from waste gases, such as smelter gases, flue gases, or stack gases with subsequent recovery and recycle of absorbent materials used in the treating process.
Contamination of the atmosphere by oxides of sulfur and nitrogen has been a public health problem for many years, because of the effect on the human respiratory system, on plant life, and corrosive attack on many metals, fabrics, and building materials. Many methods have been proposed for removing oxides of sulfur and nitrogen from waste gases. Such processes range from simply scrubbing the waste gases with water or aqueous solutions or suspensions of suitable absorbents to processes involving the use of solid absorbents which, when spent or saturated, can be processed for recovery of valuable materials, regenerated for recycle or removed from the process for disposal.
Many of the prior art proceses suffer disadvantages. Some of these processes are inefficient in removal of the oxides of sulfur and nitrogen from the waste gases. Other of the processes are more efficient in removal of oxides from the waste gases but require elaborate means of treatment or regeneration of spent absorbent, such as electrolysis, oxidation, or high temperature calcination, as well as, expensive treatment prior to disposal, use, or sale of by-products. This invention overcomes many of the disadvantages known in the prior art processes by providing for efficient removal of oxides of nitrogen and sulfur from waste gases, simplified and less expensive regeneration means for spent absorbent, as well as, recovery of by-products in forms which are readily usable or marketable.
It is therefore an object of this invention to provide a method for treating waste gases to remove contaminants. It is another object of this invention to provide a method for the removal of sulfur oxides and nitrogen oxides from stack gases by treatment with an absorbent containing manganese dioxide. It is another object of this invention to provide a method for recovering manganese dioxide from absorbent spent in treating waste gases.
Other aspects, objects and the various advantages of this invention will become apparent upon reading the specification, studying the drawing, and studying the appended claims.